New liquid crystal compound preparation and application

ABSTRACT

The invention relates to liquid-crystalline compounds of the formula (I) having a —CF 2 0- bridge. The invention also relates to liquid-crystalline media prepared therewith and to liquid-crystal display devices (LC displays) containing these media. This kind of compounds has the excellent characteristics including a large dielectric anisotropy, fast response time and high clearing point, and good miscibility at low temperature in the same time which has important significance in new TFT LC mixture.

The present invention relates to a kind of liquid-crystalline compoundsthat has Cycloalkyl terminal group and a —CF₂0- bridge. The preparationand application of these new compounds are also included. The inventionalso relates to liquid-crystal display devices (LC displays) containingthese media.

Liquid crystals are used principally as dielectrics in display devices,since the optical properties of such substances can be modified by anapplied voltage. Electro-optical devices based on liquid crystals areextremely well known to the person skilled in the art and be based onvarious effects. Examples of such devices are cells having dynamicscattering, DAP(deformation of aligned phase) cells, guest/host cells,TN cells having a twisted nematic structure, STN (supertwisted nematic)cells, SBE(super birefringence effect) cells and OMI (optical modeinterference) cells.

Thin-film transistors (TFTs) matrix is principally applied to TN(twisted nematic) mode, IPS (H-Plane Switching) mode/FFS(Fringe FieldSwitching) mode, VA (Vertical Alignment) mode, and other display modes.

After decades of accumulation and development, TFT (thin-filmtransistor) technology is getting more mature, but the demand fordisplay technology is constantly improving. In order to get the superiorpicture quality, liquid crystal monitors are required to achieve morerapid response, brighter colors and wider color gamut. The drive voltageshould be lower to reduce power consumption. As one of the mostimportant optoelectronic materials used in LCD, liquid crystal materialplays an important role of improving the performance of the liquidcrystal displays.

Fast response is required for the LCD, in order to avoid the imagesticking or smearing when dynamic pictures are displaying. Thus a lowerrotational viscosity of liquid crystal material is required.Furthermore, in order to reduce energy consumption of devices, the drivevoltage should be lower. So improving the dielectric anisotropy of theliquid crystal makes great significance.

The liquid crystal material must have good chemical stability, thermalstability, good electric and electromagnetic radiation stability.Furthermore, the liquid crystal materials should have a low viscosity,short addressing times, low threshold voltage and high contrast ratio.LC is generally used as a mixture of several components, it is importantthat these components easily miscible with each other. Other properties,such as conductivity, dielectric anisotropy and optical anisotropyshould also meet the applications requirements. For example, the liquidcrystal used in twisted nematic structure should have a positivedielectric anisotropy and low electrical conductivity.

It is important to develop single liquid crystal materials of a superiorperformance, since the properties of the single liquid crystal directlydetermine the properties of liquid crystal mixture. The single havingthe chemical structure of Difluoromethoxy bridge not only has highdielectric anisotropy, but also has the superiority to low therotational viscosity.

The present invention provides a medium, especially for MLC, IPS, TN orSTN displays of this type, which preferably simultaneously have highspecific resistance values and low threshold voltage. This objectrequires liquid-crystalline compounds which have a high clearing pointand low rotational viscosity.

It has now been found that this object can be achieved if theliquid-crystalline compounds according to the invention are used.

The invention thus relates to liquid-crystalline compounds of theformula I

in which Cycloalkyl denotes cyclobutyl, cyclopentyl and cycloheptyl,[L]p denotes CH₂ or 0, and [L]p contains one 0 at most,

-   X₁ and X₂ each, independently of one another, denote H or 0    alternatively, and X₁ or X₂ denote 0 at the least,-   A₁ and A₂ each, denotel, 4-cyclohexylidene, 1,4-phenylene or    fluoro-1,4-phenylene,-   Z₁ denotes —CH₂—, —CH₂CH₂—, —(CH₂)₃—, —(CH₂)₄—, —CH—CH—, —C≡C—,    —C00-, -00C—, —CF₂0-, -0CH₂—, —CH₂0-, -0CF₂—, —CF₂CH₂—, —CH₂CF₂—,    —C₂F₄—, —CF═CF— or a single bond,-   Y₁, Y₂ denote H or F alternatively,-   R denotes H, F, CL, CF₂, CHF₂, 0CF or 0CHF₂,-   p denotes 0-6, m denotes 0, 1, 2 or 3, n denotes 0 or 1.

The invention furthermore relates to the use of the compounds of theformula I in liquid-crystalline media.

The invention relates, in particular, to the compounds of the formula Iin which Cycloalkyl denotes cyclobutyl or cyclopentyl, X₁ denotes 0 andX₂ denotes H, or X₁ and X₂ denotes 0 independently, R denotes F or 0CF₃,m+n1 or 2, when n=0, Z₁ independently denotes single bond, and Y₁, Y₂each, independently of one another, denote H or F, p=0.

Particularly preferred compounds of the formula I are the compounds ofthe formula IA-1 to ID-43.

The compounds of the formula I are prepared by methods known per se, asdescribed in the literature (for example in the standard works, such asHouben-Weyl, Methoden der organischen Chemie [Methods of OranicChemistry], Georg-Thieme-Verlag, Stuttgart), to be precise underreaction conditions which are known and suitable for the said reactions.Use can also be made here of variants which are known per se, but arenot mentioned here in greater detail.

The compounds of the formula I can be prepared, for example, as follows:

The media according to the invention are preferably based on a pluralityof (preferably two, three or more) compounds of the formula I , i. e.The proportion of these compounds is 5-95%, preferably 10-60% andparticularly preferably in the range 15-40%.

The individual compounds of the formula I to V and their sub-formulawhich can be used in the media according to the invention are eitherknown or they can be prepared analogously to the known compounds.

Preferred embodiments are indicated below:

The medium preferably comprises one, two or three homologous compoundsof the formula I, where each homologue is present in the mixture in amaximum amount of 10%.

Medium additionally comprises one or more compounds selected from thegroup consisting of the general formula II to V:

in which the individual radicals have the following meanings:

R₁, R₂, R₃, R₄, R₅ each, independently of one another, denote one of H,alkyl having 1-10 C atoms, alkoxy having 1-10 C atoms, alkenyl having2-10 C atoms, alkenyloxy having 3-8 C atoms,or one or more H arefluorine-substituted alkyl having 1-10 C atoms, alkoxy having 1-10 Catoms, alkenyl having 2-10 C atoms, alkenyloxy having3-8 C atoms atleast.

R₆, Y₆, Y₈ each, are one of the radicals listed below:

{circle around (1)}: —H, —Cl, —F, —CN, -0CN, -0CF₃, —CF, —CHF, —CH₂F,-0CHF₂, —SCN, —NCS, —SF₅,

{circle around (2)}: Alkyl has 1-15 C atoms, alkoxy has 1-15 C atoms,alkenyl has 2-15 C atoms, or alkenyloxy has 2-15 C atoms,

{circle around (3)}: The radicals mentioned in {circle around (2)}, oneor more —CH₂— are substituted by —CH═CH—, —C≡C—, —C00-, -00C—,cyclobutane, cyclopentane, -0-, or —S— and 0 atoms don't link directly,

{circle around (4)}: The radicals mentioned above {circle around (2)}and {circle around (3)}, one or more H are substituted by F or CL,

X₆ denotes —H or —F,

Z₂, Z₃, Z₄, Z₅ denote single bond, or —CH₂—, —CH₂—CH₂—, —(CH₂)₃—,—(CH₂)₄—, —CH═CH—, —C≡C—, —C00-, -00C—, —CF₂0-, -0CH₂—, —CH₂0-, -0CF₂—,—CF₂CH₂—, —CH₂CF₂—, or —CF═CF—,

each, independently denote single bond,

o, k, q, r, s, t denote 0-3, and q+r≦5, s+t≦5.

A LC mixture have polar singles containing a —CF₂0- bridge of claim 1,wherein the proportion of the compounds of the formula I in the mixtureas a whole is 5 to 60%, the proportion of the compounds of the formulaII in the mixture as a whole is 10 to 60%, the proportion of thecompounds of the formula Min the mixture as a whole is 5 to 35%, theproportion of the compounds of the formula IV in the mixture as a wholeis 5 to 30%, the proportion of the compounds of the formula V in themixture as a whole is 5 to 30%. The proportion of the compounds of theformula I toVas a whole is 100%. And the optically active compound0˜0.5% of the proportion of the compounds of the formula I to a whole.

The following examples are intended to explain the invention withoutrestricting it. Above and below, percentages are percent by weight. Alltemperatures are given in degrees Celsius. Cp. denotes clearing point.Furthermore, C=crystalline state, N=nematic phase, S=semcitc phase andI=isotropic phase. The data between these symbols represent thetransition temperatures. An denotes optical anisotropy (589 nm, 25° C.),Δ ε the dielectric anisotropy (1 kHz, 25° C.).The rotational viscosityγ, (mPa·s) is likewise determined at 25° C., VHR (%) denotes voltagehold ratio (5V, 60 Hz, 20° C.), ρ (×10¹³ Ω·cm) denotes electricalresistivity (20° C.).

EXAMPLE 1

-   Step 1.1

100 mmol of 1-a is dissolved in 30 ml of ether, and 100 mmol ofcyclohexylamine and 60 mmol of potassium carbonate is added and stirredat room temperature for 8 hours. After cooling, the batch is filteredwith a G5 sand core funnel which covered with a layer of 5 mm diatomite,the suspension is distillated under reduced pressure. 18 g of yellowoily liquids is gotten, and dissolved it in 250 mmol of ethyl acrylate,meanwhile 0.4 g of p-dihydroxy benzene is added, and the mixture isrefluxed at 105° C. for 10 hours. Placed it to room temperature, 300 mlof THF is added and 200 ml of saturated oxalic acid aqueous solution isadded dropwise, then the organic phase is extracted twice with 50 ml ofether, and the mixture is washed twice with 50 ml of water. The solutionis dried with anhydrous magnesium sulfate, and filtered to separate thedrying agent. The mixture is evaporated to dryness in a rotaryevaporator, giving 19.5 g of brown residue. The residue ischromatographyed over silica gel, giving 12.5 g yellow oily liquids 1-b.Yield: 63.0%.

-   Step 1.2

The 63 mmol of 1-b gotten from the first step is dissolved in 120 ml ofpropyl alcohol, and 69 mmol of crano sodium borohydride is added. Afterstirring for 3 hours at room temperaturethe mixture is adjusted to pH-3by addition of 2 mol/LHCL. 100 ml of water is added to the reactionsolution and extracted twice with 50 ml of methylbenzene, the organicphase is washed twice with 40 ml of water and dried with anhydrousmagnesium sulfate. The organic phase is evaporated in a rotaryevaporator. The residue is chromatographyed over silica gel, giving 6.6g of yellow transparent liquids 1-c. Yield: 68.0%.

-   Step 1.3

43 mmol of paradibromobenzene in 30 ml of THF are added dropwise to asolution of 45 mmol of magnesium chips in 30 ml of THF and get Grignardreagent. 43 mmol of 1-c in 20 ml of THF are added dropwise and refluxedfor 1.5 hours. The mixture is poured into dilute HCL, and the aqueousphase is extracted with methylbenzene. The organic phase is washed toneutral and evaporated. 50 ml of methylbenzene and 0.5 gtoluene-p-sulfonic acid are added to the product and refluxed to get ridof the water. Then petroleum ether is added to dissolve the crudeproduct and chromatographyed over silica gel and subsequentlyrecrystallised, giving 11.7 g of 1-d, Yield: 93.2%.

-   Step 1.4

A mixture of 40 mmol of 1-d, 60 ml of methylbenzene, 80 ml of ethanoland 1 g of Raney's nickel is vibrated for 6 hours to hydrogenation atroom temperature and constant pressure. Then the mixture is filtered andthe residual is evaporated, giving 11.6 g 1-e. Yield: 98.3%.

-   Step 1.5

0.4 mmol of Pd (PPh₃)₄ is added to the mixture of 39 mmol of 1-e, 43mmol of 3,5-diflurophenylo boric acid, 40 ml of methylbenzene, 40 ml ofethanol, 150 ml of water, 2.6 g (0.24 mol) of sodium carbonate undernitrogen atmosphere. The mixture is heated to reflux for 5 hours. Theaqueous phase is extracted with methylbenzene. The organic phase iswashed with water to neutral and evaporated. The crude product isdissolved in 40 ml of petroleum ether and chromatographyed over silicagel, evaporated, subsequently recrystallised in 60 ml of ethanol, givingyellow crystal 1-f 11.8 g. Yield: 92.3%.

-   Step 1.6

57 mmol of BuLi (15% in hexane) is added dropwise to the mixture of 36mmol of 1-f, 50 ml of THF in 1 hour under nitrogen atmosphere at −60° C.The mixture is stirred for half an hour. Then the solution of 42 mmolDifluorodibromomethane in 20 ml THF is added dropwise to the mixture inhalf an hour at the same temperature. Then allowed to come to −40° C.(in 2 hours) and poured it to 2 ml of HCL in 33 ml of water, and theaqueous phase is extracted with petroleum ether once. The organic phaseis washed to neutral with salt solution and evaporated. The crude yellowoily liquid is dissolved in petroleum ether and chromatographyed oversilica gel, evaporated, giving 13. 2 g of yellow solid 1-g. Yield: 55.6%.

-   Step 1.7

A mixture of 20 mmol of 1-g, 23 mmol of 3,4,5-Trifluoro phenol, 43 mmolof potassium carbonate, 80 ml of dimethyl sulfoxide are stirred at 60°C. for 3 hours. Then the mixture is poured into 150 ml of water, and theproduct is extracted with 30 ml petroleum ether twice. The resultingorganic layer is washed with water and chromatographed over silica geland subsequently recrystallised fourth from petroleum ether, givingwhite crystal 6. 3 g 1-h. Yield :60.1% C 101.2 N 134.5 I; Δn−0.139;Δε−27.2.

Example 2

-   Step 2.1

The method is as same as the Example 1, the crude material is changed tocyclopentyl acetaildehyde giving 6.72 g of 2-b at last.

-   Step 2.2

40 mmol of paradibromobenzene in 30 ml of THF are added dropwise to asolution of 42 mmol of magnesium chips in 30 ml of THF and get Grignardreagent. 40 mmol of 2-b in 20 ml of THF are added dropwise and refluxedfor 1.5 hours. The mixture is poured into dilute HCL, and the aqueousphase is extracted with methylbenzene. The organic phase is washed toneutral and evaporated. 50 ml of methylbenzene and 0.5 gtoluene-p-sulfonic acid are added to the product and refluxed to get ridof the water. Then petroleum ether is added to dissolve the crudeproduct and chromatographyed over silica gel and subsequentlyrecrystallised, giving 6.1 g of 2-d. Yield: 96.5%.

-   Step 2.3

A mixture of 6.1 g of 2-d, 30 ml of methylbenzene, 40 ml of ethanol and1 g of Raney's nickel is vibrated for 6 hours to hydrogenation at roomtemperature and constant pressure. Then the mixture is filtered and theresidual is evaporated, giving 5.8 g 2-e. Yield: 98.2%.

-   Step 2.4

0.2 mmol of Pd (PPh3)4 is added to the mixture of 19 mmol of 2-e, 21mmol of 3,5-diflurophenylo boric acid, 20 ml of methylbenzene, 20 ml ofethanol, 60 ml of water, 0.24 mol of sodium carbonate under nitrogenatmosphere. The mixture is heated to reflux for 5 hours. The aqueousphase is extracted with 100 ml methylbenzene. The organic phase iswashed with water to neutral and evaporated. The crude product isdissolved in 20 ml of petroleum ether and chromatographyed over silicagel, evaporated, subsequently recrystallised in 30 ml of ethanol, givingyellow crystal 2-g5.8 g. Yield: 90.0%.

-   Step 2.5

27.5 mmol of BuLi (15% in hexane) is added dropwise to the mixture of 17mmol of 2-g, 20 ml of THF in 1 hour under nitrogen atmosphere at −60° C.The mixture is stirred for half an hour. Then the solution of 20 mmolDifluorodibromomethane in 7 ml THF is added dropwise to the mixture inhalf an hour at the same temperature. Then allowed to come to −40° C.(in 2 hours) and poured it to 2 ml of HCL in 33 ml of water, and theaqueous phase is extracted with petroleum ether once. The organic phaseis washed to neutral with salt solution and evaporated. The crude yellowoily liquid is dissolved in petroleum ether and chromatographyed oversilica gel, evaporated, giving 6.9 g yellow solid 2-h. Yield: 70.6%.

-   Step 2.6

A mixture of 12 mmol of 2-h, 14 mmol of 3, 4,5-Trifluoro phenol, 26 mmolof potassium carbonate, 50 ml of dimethyl sulfoxide are stirred at 60°C. for 3 hours. Then the mixture is poured into 100 ml of water, and theproduct is extracted with 15 ml petroleum ether twice. The resultingorganic layer is washed with water and chromatographed over silica geland subsequently recrystallised fourth from petroleum ether, givingwhite crystal 3.2 g 1-h. Yield:50.4% C 118.2 N 156.31; Δn=0.148; Δε=28.4.

The following compounds of the formula are prepared analogously:

EXAMPLE 3

-   Step 3.1

250 ml of 3-a and 1 mol of 2-cyclopentyl-1,3-propylenediol are dissolvedin 300 ml of methylbenzene, and 8 mmol of p-toluenesulfonic acid isadded. The mixture is heated to reflux and stirred for 4 hours. Themixture evaporated to dryness in a rotary evaporator. The residue ispurified by column chromatography (silica gel/petroleum ether), giving25.4 g of yellow oily liquids 3-b. Yield: 81.6%.

-   Step 3.2

200 mmol of 3-b is dissolved in 500 ml of THF and cooled to −70° C.Firstly 200 mmol of BuLi (15% in hexane) followed by 200 mmol oftrimethyl borate in150 ml of THF are added dropwise. The mixture isallowed come to −30° C., adjusted to pH=2 by addition of 2 mol/L HCl andsubjected to aqueous work-up. The crude product is digested with hotpetroleum ether and crystallized at 0° C., giving 41.2 g of white solid3-c. Yield: 74.6%.

-   Step 3.3

A mixture of 9 mmol of 3-c, 149 mmol of 3-d, 0.4 mmol of Pd (PPh₃)₄, 600ml of methylbenzene and 600 ml of Na borate buffer (pH=9) is stirred at80° C., for 20 hours. The mixture is poured into 0.3 mol/L HCL 100 ml,and the product is extracted with CH₂Cl₂, dried over Na₂S0₄ andevaporated to dryness in a rotary evaporator. The crude product ispurified by column chromatography (silica gel/petroleum ether) andsubsequently recrystallised from petroleum ether at −20° C., giving 74.2 g of 3-e. Yield: 92. 2%. C 132 N 168.2 I; 4 Δn=0. 1346; Δ ε−29.2.

The following compounds of the formula are prepared analogously:

EXAMPLE 4

Use the 2-e gotten from Example 2 as the crude material.

-   Step 4.1

80 mmol of 2-e is dissolved in 200 ml of THF and cooled to −70° C.Firstly 80 mmol of BuLi (15% in hexane) followed by 80 mmol of trimethylborate in 60 ml of THF are added dropwise. The mixture is allowed cometo −30° C., adjusted to pH-2 by addition of 2 mol/L HCL and subjected toaqueous work-up. The crude product is digested with hot heptanes andcrystallized at 0° C., giving 17.5 g of white solid.Yield:79.8%.

-   Step 4.2

A mixture of 60 mmol of 4-a, 300 ml of methylbenzene, 120 mmol of NaOH,50 ml of water and 30 ml of 30% H₂O₂ is stirred at 45° C. for 2 hours.The mixture is adjusted to pH=2 by addition of 10% HCL and subjected toaqueous work-up. The crude product is recrystallised from heptane,giving 6.7 g of white crystal. Yield: 45.4%.

-   Step 4.3

27 mmol of 4-b is hydrogenated at 15 MP pressure and130° C. for 10 hoursin 100 ml solution (methylbenzene:ethanol-1:5) in the presence of 1.5 gof Raney's nickel catalyst. Conventional work-up gives 6.4 g of whitesolid 4-c. Yield: 94.1%.

-   Step 4.4

25 mmol of 4-c is dissolved in 50 ml of methylbenzene, and 20 ml of 30%H₂0₂ is added. The mixture stirred at 45° C. for 2 hours. Then themixture is distillated under reduced pressure, giving 5. 5 g ofcolorless oily liquid 4-d. Yield: 88.0%.

-   Step 4.5

24. 2 mmol of BuLi (15% in hexane) are added into 24.2 mmol of2-trimethylsilyl-1,3-dithiane in 80 ml of THF at −70° C. After 4 hours,the mixture is allowed to −10° C., and then cooled to −78° C. A solutionof 22 mmol of 4-d in 25 ml of THF are added, the mixture is allowed tocome to room temperature and stirred for 15 hours. After conventionalwork-up, the crude product is recrystallised from heptane, giving 3.27 gof colorless solid 4-e. Yield: 42.3%.

-   Step 4.6

9.5 mmol of trifluoromethanesulfonic acid are added dropwise at −20° Ctoa solution of 9.3 mmol of 4-e in 60 ml of CH₂Cl₂. The mixture is allowedto come to room temperature for 30 minutes and then cooled to −78° C.Firstly a solution of 14 mmol of 3,4,5-Trifluoro phenol and 15.4 mmol oftrithylamine in 30 ml of CH₂Cl₂ and 5 minutes later 38 mmol oftriethylamine tris(hydrofluoride) are added. Then a solution of 39 mmolof Br₂ in 40 ml of CH₂Cl₂ is added. The mixture is stirred at −70° C.for 1 hour. The reaction mixture is allowed to come to −10° C., and ispoured into 450 ml of 4 mol/L ice-cold NaOH. The mixture is subjected toconventional aqueous work-up, and the crude product is purified bychromatography on silica gel (heptanes/MTB ether 1:1) and recrystallisedfrom petroleum ether at −50° C., giving 1.6 g of colorless solid 4-f.Yield is 39.8%. C 55.2 N 80.51; Δn=0.0640; Δ ε=14.6.

The following compounds of the formula are prepared analogously:

EXAMPLE 5

-   Step 5.1

100 mmol of 5-a and 400 mmol of 2-cyclopentyl-1,3-propylenediol aredissolved in 100 ml of methylbenzene, 0.9 g of p-toluenesulfonic acid isadded, then heat to reflux, and stirred for 4 hours. The mixtureevaporated to dryness in a rotary evaporator. The mixture is purified bychromatography on silica gel with petroleum ether, giving 23.9 gcolorless oil 5-b. Yield: 89.3%.

-   Step 5.2

130 mmol of BuLi (15% in hexane) are added dropwise at −60° C. to asolution of 89 mmol of 5-b in 120 ml of THF under nitrogen atmosphere.The mixture is stirred for a further 30 minutes at the same temperature.A solution of 107 mmol of Difluorodibromomethane in 100 ml of THF isthen added dropwise at the same temperature, and the mixture is stirredfor a further 30 minutes, allowed to come to −40° C. The mixture ispoured into 100 ml of 2 mol/L HCL, the product is extracted with 100 mlpetroleum ether. The resulting organic layer is washed with water, driedover Na₂S0₄ and evaporated to dryness in a rotary evaporator. The crudeproduct is chromatographed over silica gel in petroleum ether, giving25.7 g of yellow solid 5-c. Yield: 72.8%.

-   Step 5.3

A mixture of 64 mmol of 5-c, 76 mmol of 3,4,5-Trifluoro phenol, 160 mmolof potassium carbonate, 250 ml of dimethyl sulfoxide are stirred at 60°C. for 3 hours. Then the mixture is poured into 500 ml of water, and theproduct is extracted with 150 ml petroleum ether twice. The resultingorganic layer is washed with water, dried over Na₂S0₄ and evaporated todryness in a rotary evaporator. The residue is chromatographed oversilica gel in petroleum ether and subsequently recrystallised twice frompetroleum ether at −20° C., giving 19.2 g of 5-d. Yield: 64.8%. C 52.1 N93.2 I; Δn=0.081; Δ ε=17.8.

The following compounds of the formula are prepared analogously:

EXAMPLE 6

-   Step 6.1

105 mmol of Magnesium-chips in 70 ml of THF are reacted with 100 mmol of1-bromo-3,5-difluorobenzene in 70 ml of THF at boiling heat. After theaddition of the 1-bromo-3,5-difluorobenzene, the reaction mixture isrefluxed conditions of a Grignard reaction for 30 min. Afterwards 40mmol 6-a in 50 ml of THF are added dropwise. The mixture is stirred fora further 1.5 hours at the same temperature. Then the reaction solutionis cooled to room temperature, poured into 100 ml of 1 mol/L HCL, theproduct is extracted with 50 ml of methylbenzene. The resulting organiclayer is washed with water, dried over Na₂S0₄ and evaporated to drynessin a rotary evaporator. The residue was dissolved in 120 ml ofmethylbenzene, 0.8 g of p-toluenesulfonic acid is added, then heat toreflux, and stirred for 8 hours. The mixture evaporated to dryness in arotary evaporator. The mixture is purified by chromatography on silicagel with petroleum ether to get a colorless solid. Then the solid ishydrogenated at 40° C. For 8 hours in 60 ml of methylbenzene and 30 mlof ethanol in the presence of 1.5 g of water-moist 5% Pd/C catalyst.Conventional work-up gives a colorless solid 32.2 g 6-c. Yield: 96.4%.

-   Step 6.2

150 mmol of BuLi (2. 5 mol/L in hexane) are added dropwise at −60° C. toa solution of 96 mmol of 6-c in 120 ml of THF, under nitrogenatmosphere, the mixture is stirred for a further 30 minutes at the sametemperature. A solution of 113 mmol of Difluorodibromomethane in 60 mlof THF is then added dropwise at the same temperature, and the mixtureis stirred for a further 30 minutes, allowed to come to −40° C. Themixture is poured into 300 ml of 2 mol/L HCL, the product is extractedwith petroleum ether. The resulting organic layer was washed with water,dried over Na2S0₄ and evaporated to dryness in a rotary evaporator. Thecrude product is chromatographed over silica gel in petroleum ether,giving colorless solid 29.5 g of 6-d. Yield: 66.4%.

-   Step 6.3

A mixture of 63 mmol of 6-d, 74 mmol of 3,4,5-Trifluoro phenol, 130 mmolof potassium carbonate, 250 ml of dimethyl sulfoxide are stirred at 60°C. for 3 hours. Then the mixture is poured into 100 ml of water, and theproduct is extracted with 70 ml petroleum ether twice. The resultingorganic layer is washed with water, dried over Na₂S0₄ and evaporated todryness in a rotary evaporator. The residue is chromatographed oversilica gel in petroleum ether and subsequently recrystallised twice frompetroleum ether at −20° C., giving 22. 4 g 6-e. Yield :66. 7% C 135. 2N162.2 I; Δn=0.138; Δ ε=22.3.

The following compounds of the formula are prepared analogously:

Mixture Examples

Mixture 1

 

 

28%           5%         5% S—N (° C.): ≦ −40 Cp (° C.): 100 γ 1(mPa•s): 99.8 Δn: 0.112 Δε: 11.3 V₁₀ (V): 1.54 V₉₀ (V): 2.47 τ (ms, 4V): 9.23 ρ (× 10¹³ Ω • cm): 15.2 VHR (%): 99.85

3%

7%

3%

2%

5%

5%

3%

5%

5%

10% 

11% 

3%

Mixture 2

 

 

13%          15%          6% S—N (° C.): ≦ −40 Cp (° C.): 96 γ 1(mPa•s): 77.7 Δn: 0.100 Δε: 6.5 V₁₀ (V): 1.98 V₉₀ (V): 3.03 τ (ms, 4.5V): 10.50 ρ (× 10¹³ Ω • cm): 29.0 VHR (%): 99.86

8%

1%

3%

4%

7%

7%

5%

27% 

2%

2%

Mixture 3

 

 

16%          12%          10%  S—N (° C.): ≦ −40 Cp (° C.): 90 γ 1(mPa•s): 80.0 Δn: 0.100 Δε: 5.5 V₁₀ (V): 1.88 V₉₀ (V): 3.02 τ (ms, 4.5V): 8.30 ρ (× 10¹³ Ω • cm): 25.9 VHR (%): 99.72

3%

3%

3%

4%

7%

8%

2%

20% 

6%

6%

Mixture 4

 

 

20%          3%         5% S—N (° C.): ≦ −40 Cp (° C.): 85 γ 1 (mPa•s):80.6 Δn: 0.098 Δε: 8.0 V₁₀ (V): 1.58 V₉₀ (V): 2.64 τ (ms, 4.5 V): 12.10ρ (× 10¹³ Ω • cm): 18.0 VHR (%): 99.65

3%

3%

5%

7%

8%

4%

2%

3%

7%

5%

10% 

7%

8%

Mixture 5

 

 

29%          7%         3% S—N (° C.): ≦−40 Cp (° C.): 100 γ 1 (mPa•s):90.5 Δn: 0.100 Δε: 10.0 ρ (× 10¹³ Ω • cm): 25.2 VHR (%): 99.75 V₁₀ (V):1.91 V₉₀ (V): 2.96 τ (ms, 4.5 V): 20.40

2%

5%

8%

2%

4%

5%

3%

5%

6%

8%

8%

5%

Mixture 6

 

 

37%          8%         8% S—N (° C.): ≦ −40 Cp (° C.): 100 γ 1 (mPa•s):87.7 Δn: 0.112 Δε: 8.5 ρ (× 10¹³ Ω • cm): 27.9 VHR (%): 99.80 V₁₀ (V):1.61 V₉₀ (V): 2.59 τ (ms, 4.5 V): 19.30

3%

4%

4%

3%

2%

4%

7%

8%

6%

6%

Mixture 7

 

 

15%        5%               7% S—N (° C.): ≦ −40 Cp (° C.): 110 γ 1(mPa•s): 95 Δn: 0.100 Δε: 7.8 V₁₀ (V): 1.64 V₉₀ (V): 2.61 τ (ms, 4.5 V):25.80 ρ (× 10¹³ Ω • cm): 19.10 VHR (%): 99.7

8%

5%

6%

4%

5%

10% 

7%

12% 

6%

10% 

Mixture 8

 

 

23%          5%          6% S—N (° C.): ≦ −40 Cp (° C.): 97 γ 1 (mPa•s):90.1 Δn: 0.111 Δε: 8.4 V₁₀ (V): 1.56 V₉₀ (V): 2.57 τ (ms, 4 V): 9.50 ρ(× 10¹³ Ω • cm): 21.3 VHR (%): 99.67

 6%

 6%

 5%

 5%

 8%

10%

21%

 5%

Mixture 9

 

 

13%          4%              9% S—N (° C.): ≦ −40 Cp (° C.): 100 γ 1(mPa•s): 88.1 Δn: 0.110 Δε: 8.3 V₁₀ (V): 1.87 V₉₀ (V): 3.00 τ (ms, 4.5V): 11.70 ρ (× 10¹³ Ω • cm): 26.2 VHR (%): 99.8

 7%

 7%

11%

17%

 6%

11%

 4%

11%

Mixture 10

 

 

29%         17%         14% S—N (° C.): ≦ −40 Cp (° C.): 100 γ 1(mPa•s): 90.4 Δn: 0.099 Δε: 9.8 V₁₀ (V): 1.45 V₉₀ (V): 2.51 τ (ms, 4.5V): 9.80 ρ (× 10¹³ Ω • cm): 25.4 VHR (%): 99.75

 5%

 7%

 5%

 4%

11%

 8%

Mixture 11

 

 

19%         14%          5% S—N (° C.): ≦ −40 Cp (° C.): 96 γ 1 (mPa•s):98.7 Δn: 0.098 Δε: 10.5 V₁₀ (V): 1.35 V₉₀ (V): 2.45 τ (ms, 4.0 V): 11.80ρ (× 10¹³ Ω • cm): 27.4 VHR (%): 99.84

 6%

 9%

13%

23%

11%

Mixture 12

 

 

25%          4%             7% S—N (° C.): ≦ −40 Cp (° C.): 101 γ 1(mPa•s): 92 Δn: 0.112 Δε: 8.9 V₁₀ (V): 1.85 V₉₀ (V): 2.90 τ (ms, 4.5 V):14.50 ρ (× 10¹³ Ω • cm): 25.8 VHR (%): 99.82

4%

7%

8%

9%

14% 

13% 

9%

Mixture 13

 

 

38%         12%          8% S—N (° C.): ≦ −40 Cp (° C.): 99 γ 1 (mPa•s):90.5 Δn: 0.100 Δε: 6.3 V₁₀ (V): 1.95 V₉₀ (V): 3.05 τ (ms, 4.5 V): 12 ρ(× 10¹³ Ω • cm): 20.5 VHR (%): 99.76

12%

 6%

 1%

 5%

10%

 8%

Mixture 14

 

 

12%          2%          5% S—N (° C.): ≦ −40 Cp (° C.): 97 γ 1 (mPa•s):80.0 Δn: 0.105 Δε: 9.3 V₁₀ (V): 1.79 V₉₀ (V): 2.87 τ (ms, 4.5 V): 11 ρ(× 10¹³ Ω • cm): 20.5 VHR (%): 99.76

 4%

 8%

 5%

14%

34%

 1%

 8%

 7%

Mixture 15

 

 

21%          12%          10%  S—N (° C.): ≦ −40 Cp (° C.): 100 γ 1(mPa•s): 85 Δn: 0.110 Δε: 7.9 V₁₀ (V): 1.88 V₉₀ (V): 2.86 τ (ms, 4 V):11.60 ρ (× 10¹³ Ω • cm): 26.8 VHR (%): 99.82

11% 

7%

6%

1%

2%

7%

12% 

8%

3%

1. A liquid-crystalline compound of the formula I

Wherein Cycloalkyl denotes cyclobutyl, cyclopentyl, or cycloheptyl; [L]p denotes CH₂ or 0, wherein [L]p comprising at most one 0; X₁ and X₂, independent of one another, each denote H or 0; wherein at least one of X₁ or X₂ is 0; A₁and A₂ each, denote 1,4-cycohexylidene, 1,4-phenylene or fluoro-1,4-phenylene; Z₁ denotes —CH₂—, —CH₂—CH₂—, —(CH₂)₃—, —(CH₂)₄—, —CH═CH—, —C≡C—, —C00-, -00C—, —CF₂0-, -0CH₂—, —CH₂0-, -0CF₂—, —CF₂CH₂—, —CH₂CF₂—, —C₂F₄—, —CF═CF—, or a single bond; Y₁, Y₂ indecently denote H or F; R denotes H, F, CL, CF₃, CHF₂, OCF, or OCHF₂; and p denotes an integer between 0-6, m denotes 0, 1, 2, or 3, n denotes 0 or
 1. 2. A liquid-crystalline compound of claim 1, wherein m+n=1 or 2, wherein when n=0, Z₁ independently denotes a single bond, and Y₁, Y₂ each, independently of one another, denote H or F.
 3. A liquid-crystalline compound of claim 2, wherein Y₁ denotes F, and Y₂ denotes F or H.
 4. A liquid-crystalline compound of claim 2, wherein Y₁ and Y₂ denote F.
 5. A liquid-crystalline compound of claim 3, wherein p=0.
 6. A liquid-crystalline compound of claim 5, wherein Z₁ independently denotes a single bond.
 7. A liquid-crystalline compound of claim 6, wherein Cycloalkyl denotes cyclobutyl, X₁ denotes 0, and X₂ denotes H, or X₁ and X₂ independently denotes 0, R denotes F, as shown in formula IA.


8. A liquid-crystalline compound of claim 7, selected from the group consisting of formulae IA-1 to IA-43:


9. A liquid-crystalline compound of claim 6, wherein Cycloalkyl denotes cyclobutyl, X₁ denotes 0 and X₂ denotes H, or X₁ and X₂ independently denotes 0, R denotes 0CF₃, as shown in formula IB.


10. A liquid-crystalline compound of claim 9, selected from the group consisting of formulae IB-1 to IB-43:


11. A liquid-crystalline compound of claim 6, wherein Cycloalkyl denotes cyclopentyl, X₁ denotes 0 and X₂ denotes H, or X₁ and X₂ independently denotes 0, R denotes F, as shown in formula IC.


12. A liquid-crystalline compound of claim 11, selected from the group consisting formulae IC-1 to IC-43:


13. A liquid-crystalline compound of claim 6, wherein Cycloalkyl denotes cyclopentyl, X₁ denotes 0 and X₂ denotes H, or X₁ and X₂independently denotes 0, R denotes OCF₃, as shown in formula ID.


14. A liquid-crystalline compound of claim 13, selected from the group consisting formulae ID-1 to ID-43:


15. A liquid-crystalline medium base on a mixture of positive dielectric anisotropy, characterized in that it contains one or more compounds of the formula I :

Wherein Cycloalkyl denotes cyclobutyl, cyclopentyl, or cycloheptyl; [L]p denotes CH₂ or 0, wherein [L]p comprising at most one 0; X₁ and X₂, independent of one another, each denote H or 0; wherein at least one of X₁ or X₂ is 0; A₁ and A₂ each, denote 1,4-cyclohexylidene, 1,4-phenylene or fluoro-1,4-phenylene; Z₁ denotes —CH₂—, —CH₂CH₂—, —(CH₂)₃—, —(CH₂)₄—, —CH═CH—, —C≡C—, —C00-, -00C—, —CF₂0- , —CH₂0-, 0CF₂—, —CF₃CH₂—, —CH₂CF₂—, C₂F₄—, —CF═CF—, or a single bond; Y₁, Y₂ indecently denote H or F; R denotes H, F, CL, CF₂, CHF₂, OCF₂, or OCHF₂; and p denotes an integer between 0-6, m denotes 0, 1, 2, or 3, n denotes 0 or
 1. 16. The liquid-crystalline medium according to claim 15 wherein m+n=1 or 2, when n=0, Z₁ independently denotes a single bond, and Y₁, Y₂ each, independently of one another, denote H or F.
 17. The liquid-crystalline medium according to claim 16 wherein Y₁ denotes F, and Y₂ denotes F or H.
 18. The liquid-crystalline medium according to claim 17 wherein Y₁ and Y₂ denote F.
 19. The liquid-crystalline medium according to claim 18 wherein p=0.
 20. The liquid-crystalline medium according to claim 19 wherein Z₁ independently denotes a single bond.
 21. The liquid-crystalline medium according to claim 15 wherein it additionally comprises one or more compounds selected from the formulae II, III, IV, and V.

Wherein the individual radicals have the following meanings: R₁, R₂, R₃, R₄, R₅ each, independently of one another, denote one of H, alkyl having 1-10 C atoms, alkoxy having 1-10 C atoms, alkenyl having 2-10 C atoms, alkenyloxy having 3-8 C atoms, or one or more H are fluorine-substituted alkyl having 1-10 C atoms, alkoxy having 1-10 C atoms, alkenyl having 2-10 C atoms, alkenyloxy having 3-8 C atoms at least. R₆, Y₆, Y₈ each, are one of the radicals listed below: {circle around (1)}: —H, —CL, —F, —CN, -0CN, -0CF₃, —CF₃, —CHF₂, —CH₂F, -0CHF₂, —SCN, —NCS, —SF₅, {circle around (2)}: Alkyl has 1-15 C atoms, alkoxy has 1-15 C atoms, alkenyl has 2-15 C atoms, or alkenyloxy has 2-15 C atoms, {circle around (3)}: The radicals mentioned in {circle around (2)}, one or more —CH₂— are substituted by —CH═CH—, —C≡C—, —00-, -00C—, cyclobutane, cyclopentane, -0-, or —S— and 0 atoms don't link directly, {circle around (4)}: The radicals mentioned above {circle around (2)} and {circle around (3)}, one or more H are substituted by F or CL, X₆ denotes —H or —F, Z₂, Z₃, Z₄, Z₅ denote single bond, or —CH₂—, —CH₂—CH₂—, —(CH₂)₃—, —(C₂)₄—, —CH═CH—, —C≡C—, —C00-, -00C—, —CF₂0-, -0CH₂—, —CH₂0-, -0CF₂, CF₂CH₂—, —CH₂CF₂—, —C₂F₄— or —CF═CF—,

each, independently denote single bond,

o, k, q, r, s, t denote 0-3, and q+r≧5, s+t≧5.
 22. The liquid-crystalline medium according to claim 21 wherein it comprises 5 to 95% by weight of one or more compounds of the formula I.
 23. The liquid-crystalline medium according to claim 21 wherein it comprises 10 to 60% by weight of one or more compounds of the formula II.
 24. The liquid-crystalline medium according to claim 21 wherein it comprises 5 to 35% by weight of one or more compounds of the formula III.
 25. The liquid-crystalline medium according to claim 21 wherein it comprises 5 to 30% by weight of one or more compounds of the formula IV.
 26. The liquid-crystalline medium according to claim 21 wherein it comprises 5 to 30% by weight of one or more compounds of the formula V.
 27. A cholesteric liquid crystalline medium characterized in that it comprises as a nematic component a liquid crystalline medium according to claim 15 and as an optically active component one or more chiral dopants.
 28. Electro-optical liquid-crystal display containing a liquid-crystal medium according to claim
 15. 